Magnetic oscillations of in-plane conductivity in quasi-two-dimensional metals

Abstract

We develop the theory of transverse magnetoresistance in layered quasi-two-dimensional metals. Using the Kubo formula and harmonic expansion, we calculate intralayer conductivity in a magnetic field perpendicular to conducting layers. The analytical expressions for the amplitudes and phases of magnetic quantum oscillations (MQO) and of the so-called slow oscillations (SlO) are derived and applied to analyze their behavior as a function of several parameters: magnetic field strength, interlayer transfer integral and the Landau-level width. Both the MQO and SlO of intralayer and interlayer conductivities have approximately opposite phase in weak magnetic field and the same phase in strong field. The amplitude of SlO of intralayer conductivity changes sign at ωcτ0 = √ 3. There are several other qualitative difference between magnetic oscillations of in-plane and out-of-plane conductivity. The results obtained are useful to analyze experimental data on magnetoresistance oscillations in various strongly anisotropic quasi-2D metals.

3D – 2D Crossover and Phase Shift of Beats of Quantum Oscillations of Interlayer Magnetoresistance in Quasi-2D Metals

“…However, in a high magnetic field B z ≫ ∆F in Q2D metals, when the Landau levels (LLs) become separated and the DoS between the LLs is zero, the MQO phase of conductivity and DoS coincide. The latter follows both from the direct observations [9,35,36] and calculations [8][9][10]16,37], being supported by the simple qualitative argument that if the DoS at the Fermi level is zero the conductivity must also be zero at low temperature. However, in spite of a general understanding, the quantitative description of this phase inversion is absent.…”

“…Note that the electron mean free time τ measured from the MQO is, usually, shorter than the transport mean free time τ tr and than the mean-free time τ * arising from short-range disorder only and measured from the damping of slow magnetoresistance oscillations [13]. This difference, τ < τ * ≈ τ tr , appears because the MQO are damped not only by short-range disorder but also by long-range sample inhomogeneities which smear the Fermi energy similar to the temperature effect [9,[13][14][15][16]. The opposite case when the transport mean free time τ tr < τ ≲ τ * is also possible in heterogeneous conductors, where there are rare but strong inhomogeneities as, e.g., domain walls or linear crystal defects.…”

“…We will use the expressions for the MQO of magnetization and interlayer conductivity from Refs. [14,16,48,49] obtained in the self-consistent Born approximation. In the leading order of the expansion in powers of the Dingle factor R D0 at temperature T, the oscillating parts of the magnetization is equal to (see Equation (33) of Ref.…”

“…The interplay between the angular and quantum magnetoresistance oscillations is nontrivial [11,12] and leads to the angular modulations of MQO amplitude [12]. The so-called difference or slow oscillations (SO) of magnetoresistance [13][14][15][16] at frequency 2∆F appear and survive at much higher temperature than the usual MQO. The SO help to determine the type of disorder and give other useful information, such as the interlayer transfer integral.…”

Coherent heavy charge carriers in an organic conductor near the bandwidth-controlled Mott transition

“…However, in our experiment only one beat node was observed within the field range where the oscillations were resolved (10 T − 15 T), suggesting that the relationship 4t ⊥ / ω c 1 may be violated. At these conditions the phase γ becomes a function of B, depending on the relative magnitudes of ω c , t ⊥ , and k B T D [59][60][61]. This was taken into account in our analysis of the field-dependent amplitude; the details of fitting are given in SM [36].…”